1. Field of the Invention
This invention relates to slitting means and in particular to perforator wheels.
2. Description of the Prior Art
In one conventional form of perforator wheel, a wheel having a beveled cutting edge is provided at angularly spaced intervals with notches. Thus, as the wheel is run against a workpiece, such as a sheet of paper or cloth, the cutting edge slits the workpiece with the slots defining unslit portions of the workpiece between relatively longer slit portions. As the slots are relatively small in width, the unslit portion of the workpiece defines a relatively frangible portion which may be readily torn apart, whereby the slit edge defines a tearing edge in the sheet.
A problem arises in the manufacture of such perforator wheels where the slots are to be made relatively small in width to define relatively small nonslit portions in the tearing edge. Illustratively, slots having a width of approximately 0.030" may be readily ground in the peripheral cutting edge of the perforator wheel. However, when slots of relatively small width, such as 0.010" or smaller, are to be provided, the grinding thereof is very costly.
A number of perforating wheels are shown in the prior art. Illustratively, in United States Letters Pat. No. 170,873 of Phillip McAleer, a paper perforating machine is provided with wheels having radial slots. As discussed above, such slots provide nonslit portions in the sheet material and it is difficult to manufacture such wheels with relatively small width slots.
In United States Letters Pat. No. 1,414,239 of W. J. Warren, a wire cutter is illustrated having a pair of rotary blades which are rotated in opposite directions to effect the desired cutting of the wire.
George F. Taylor, in United States Letters Pat. No. 1,904,568, shows a disk like cutting tool having a pair of wheels for use such as in cutting glass and the like, with the wheels being formed of a mixture of cobalt and tungsten carbide, and a pair of outer metal disks.
Frank Nassar, in United States Letters Pat. No. 3,152,501, shows a paper perforating attachment for printing presses wherein the perforating wheel, which comprises a hardened steel wheel, has a plurality of radial slots.
Kenneth T. Buttery, in United States Letters Pat. No. 3,255,648 and 3,255,649 discloses means and methods for forming weakened severance lines in paperboard products. The Buttery wheels are formed of two elements with alternating toothed portions such that secondary cuts are positioned in registry with the interstices between primary cuts, and primary cuts are positioned in registry with the interstices between the secondary cuts.
Robert P. DeTorre, in United States Letters Pat. No. 3,593,899, shows a glass-scoring process utilizing a scoring wheel having dual scoring edges in spaced side-by-side relationship.